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Title: Applications of barrier bucket RF systems at Fermilab

Abstract

In recent years, the barrier rf systems have become important tools in a variety of beam manipulation applications at synchrotrons. Four out of six proton synchrotrons at Fermilab are equipped with broad-band barrier rf systems. All of the beam manipulations pertaining to the longitudinal phase space in the Fermilab Recycler (synchrotron used for antiproton storage) are carried out using a barrier system. Recently, a number of new applications of barrier rf systems have been developed- the longitudinal momentum mining, longitudinal phase-space coating, antiproton stacking, fast bunch compression and more. Some of these techniques have been critical for the recent spectacular success of the collider performance at the Fermilab Tevatron. Barrier bunch coalescing to produce bright proton bunches has a high potential to increase proton antiproton luminosity significantly. In this paper, I will describe some of these techniques in detail. Finally, I make a few general remarks on issues related to barrier systems.

Authors:
;
Publication Date:
Research Org.:
Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
892265
Report Number(s):
FERMILAB-CONF-06-102-AD
TRN: US0701094
DOE Contract Number:
AC02-76CH03000
Resource Type:
Conference
Resource Relation:
Conference: Presented at RPIA 2006 Recent Progress in Induction Accelerators, KEK, Tsukuba, Japan, 7-10 Mar 2006
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; ACCELERATORS; ANTIPROTONS; COMPRESSION; FERMILAB; FERMILAB TEVATRON; INDUCTION; LONGITUDINAL MOMENTUM; LUMINOSITY; MINING; PERFORMANCE; PHASE SPACE; PROTONS; RF SYSTEMS; STORAGE; SYNCHROTRONS; Accelerators

Citation Formats

Bhat, C.M., and /Fermilab. Applications of barrier bucket RF systems at Fermilab. United States: N. p., 2006. Web.
Bhat, C.M., & /Fermilab. Applications of barrier bucket RF systems at Fermilab. United States.
Bhat, C.M., and /Fermilab. Wed . "Applications of barrier bucket RF systems at Fermilab". United States. doi:. https://www.osti.gov/servlets/purl/892265.
@article{osti_892265,
title = {Applications of barrier bucket RF systems at Fermilab},
author = {Bhat, C.M. and /Fermilab},
abstractNote = {In recent years, the barrier rf systems have become important tools in a variety of beam manipulation applications at synchrotrons. Four out of six proton synchrotrons at Fermilab are equipped with broad-band barrier rf systems. All of the beam manipulations pertaining to the longitudinal phase space in the Fermilab Recycler (synchrotron used for antiproton storage) are carried out using a barrier system. Recently, a number of new applications of barrier rf systems have been developed- the longitudinal momentum mining, longitudinal phase-space coating, antiproton stacking, fast bunch compression and more. Some of these techniques have been critical for the recent spectacular success of the collider performance at the Fermilab Tevatron. Barrier bunch coalescing to produce bright proton bunches has a high potential to increase proton antiproton luminosity significantly. In this paper, I will describe some of these techniques in detail. Finally, I make a few general remarks on issues related to barrier systems.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Wed Mar 01 00:00:00 EST 2006},
month = {Wed Mar 01 00:00:00 EST 2006}
}

Conference:
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  • In the Fermilab p/sup -/p colliding beam facility antiprotons are to be collected in an accumulator ring where the injection/extraction orbit length and rotation period are the same as those of the Booster Ring at T = 8 GeV, namely 474.19 m. and 1.59 X 10/sup -6/ sec. Prior to injection into the Accumulator ring the momentum spread of the antiprotons is reduced by mismatched bunch rotation in a slightly larger Debuncher ring with circumference 505.28 m and rotation period (8 GeV) 1.695 X 10/sup -6/ sec. Several of the beam manipulations in these rings are facilitated by rf systemsmore » capable of applying a longitudinal accelerating field for only part of each rotation period. The accelerating field is ''suppressed'' for the remainder of the rotation period. The concept of ''suppressed bucket'' is not new, but the use to which they are put in this project is unique. T /SUB o/ is the synchronous particle rotation period and the voltage is a single complete sinusoid of period T /SUB rf/ . The period T /SUB rf/ can be related to the rotation period by the expression T /SUB o/ = hT /SUB rf/ , where h > 1 but h need not be an integer. The repetition period of the isolated wave can be precisely T /SUB o/ (stationary) or it may differ slightly from T /SUB o/ (moving). Furthermore, the wave need not be sinusoidal as shown or even symmetric about some center point. It must only span some region T /SUB rf/ and it cannot have a dc component. Practical considerations indicate that the wave should be reasonably smooth so that the Fourier spectrum is not excessively broad.« less
  • A key issue to upgrade the luminosity of the Tevatron Run2 program and to meet the neutrino requirement of the NuMI experiment at Fermilab is to increase the proton intensity on the target. This paper introduces a new scheme to double the number of protons from the Main Injector (MI) to the pbar production target (Run2) and to the pion production target (NuMI). It is based on the fact that the MI momentum acceptance is about a factor of four larger than the momentum spread of the Booster beam. Two RF barriers--one fixed, another moving--are employed to confine the protonmore » beam. The Booster beams are injected off-momentum into the MI and are continuously reflected and compressed by the two barriers. Calculations and simulations show that this scheme could work provided that the Booster beam momentum spread can be kept under control. Compared with slip stacking, a main advantage of this new method is small beam loading effect thanks to the low peak beam current. The RF barriers can be generated by an inductive device, which uses nanocrystal magnet alloy (Finemet) cores and fast high voltage MOSFET switches. This device has been designed and fabricated by a Fermilab-KEK-Caltech team. The first bench test was successful. Beam experiments are being planned.« less
  • During the Run II era at Fermilab, the Recycler stores antiprotons at 8 GeV and the Main Injector accelerates the antiprotons and the protons from 8 GeV to 150 GeV for Tevatron injection. The Recycler injects antiprotons to the Main Injector in 2.5 MHz rf buckets. This report presents an acceleration scheme for the antiprotons that involves a slow ramp with initial 2.5 MHz acceleration and subsequent fast acceleration with 53 MHz rf system. Beam acceleration and rf manipulation with space charge and beam loading effects are simulated using the longitudinal simulation code ESME. Simulation suggests that one can expectmore » about 15% emittance growth for the entire acceleration cycle with beam loading compensations. Preliminary experimental results with proton beam will also be presented.« less
  • A novel method for beam manipulation, compression, and stacking using a broad band RF system in circular accelerators is described. The method uses a series of linear voltage ramps in combination with moving barrier pulses to azimuthally compress, expand, or cog the beam. Beam manipulations can be accomplished rapidly and, in principle, without emittance growth. The general principle of the method is discussed using beam dynamics simulations. Beam experiments in the Fermilab Recycler Ring convincingly validate the concept. Preliminary experiments in the Fermilab Main Injector to investigate its potential for merging two ''booster batches'' to produce high intensity proton beamsmore » for neutrino and antiproton production are described.« less
  • Eight tuned rf cavities have been installed and operated in the F0 straight section of the Tevatron. Their mechanical placement along the beam line enables them to be operated for colliding beams as two independent groups of four cavities, group 1-4 accelerating antiprotons and group 5-8 accelerating protons. The only difference is that the spacing between cavities 4 and 5 was increased to stay clear of the F0 colliding point. The cavities can easily be rephased by switching cables in a low-level distribution system (fan-out) so that the full accelerating capability of all eight cavities can be used during fixedmore » target operations. Likewise, the cables from capacitive probes on each cavity gap can be switched to proper lengths and summed in a fan-back system to give an rf signal representing the amplitude and phase as ''seen by the beam,'' separately for protons and antiprotons. Such signals have been used to phase lock the Tevatron to the Main Ring for synchronous transfer.« less